Electrical contacts

ABSTRACT

In relays using conductive resilient contact pads formed of fine wire to decrease contact bounce and provide contact surface wiping, damage to the fine wires by contact arcing is obviated by provision of rigid auxiliary contact surfaces which open after the fine wire surfaces open in order to diver any arcing to the rigid auxiliary contact surfaces. Several spring-operated and several magnetically operated auxiliary contact arrangements are shown.

United States Patent Inventor John 0. Kurtz I'.O. Box 79, Smithville Flats, N.Y. 13841 Appl. No. 67,468 Filed Aug. 27, 1970 Patented Oct. 12, 1971 Continuation-impart of application Ser. No. 51,932, July 2, 1970. w

ELECTRICAL CONTACTS 3 Claims, 16 Drawing Figs.

US. Cl 335/196, 200/ l 66 Int. Cl 1101b l/24 Field of Search 335/196,

177, 1l;200/l66 A, 166 H, 166 C References Cited UNITED STATES PATENTS 706,759 8/1902 Kennedy 335/196 2,164,388 7/1939 Dame........ 335/177 3,194,933 7/1965 Ramstetter.... ZOO/166 A 3,227,840 I/1966 Reed et a1 335/196 3,014,104 12/1961 Cobine et a1... 335/196 2,897,308 7/1959 Fergus 200/166 H Primary Examiner-Harold Broome Attorney-Richard G. Stephens ABSTRACT: In relays using conductive resilient contact pads formed of fine wire to decrease contact bounce and provide contact surface wiping, damage to the fine wires by contact arcing is obviated by provision of rigid auxiliary contact surfaces which open after the fine wire surfaces open in order to diver any arcing to the rigid auxiliary contact surfaces. Several spring-operated and several magnetically operated auxiliary contact arrangements are shown.

PATENTEDum 12 I97! 3,613,037

SHEET 1 BF 5 INVENTOR. 7 JOHN O. KURTZ PATENTEDnm 12 ran 3,613,037

SHEET 30F 5 ELECTRICAL CONTACTS This application is a continuation-in-part of my copending application Ser. No. 51,932 filed July 2, 1970.

The mentioned copending application discloses various forms of electrical contactors or relays which utilize one or more conductive resiliently compressible pads havinga large damping factor or low coefficient of restitution, so that relay contact bounce, chatter, mechanical shock and noise are materially reduced. The conductive pads are shown as including a plurality of fine wire sections which rub againsteach other as the pad is compressed and decompressed by opening and closing of the contacts. One form of conductive compressible pad comprises one or a few lengths of wire partially "crushed" to form a partially springy tangle, and another fonn of pad utilizes a piece of woven wire sheet formed of a plurality of fine wires.

While relays constructed as shown in the prior application are wholly satisfactory for some applications, contact arcing tends to be a problem in some applications. As a relay contact having a contact surface comprising a large number 'of fine wires opens, current flows through a decreasing number of wire sections, and just prior to complete opening all of the current may flow to only one or a few wire sections on the'face of the pad. The wire sections are desirably small in cross section in order to provide a low coefficient of restitution, but the small diameter undesirably lessens the current-carrying capacity of each wire section, thereby limiting the amount of current which may be switched without melting or welding some of the wires of the resilient pad. One object of the present invention is to provide improved relay contacts having the decreased contact bounce and other advantages of the compressible 'pads which also are capable of interrupting much larger amounts of current without damage to the compressible pads.

The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts, which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to theifollowing detailed description taken in connection with the accompanying drawings, in which:

FIG. 1 is a diagrammatic side viewof one form of relay constructed in accordance with the invention.

FIG. la is a cross section view taken at lines la-Ia in FIG. 1.

FIG. 2 is a diagrammatic side view of an alternative form of relay constructed in accordance with the invention.

FIG. 3 is a side view illustrating modified form of relay contact pair.

FIG. 3a is a cross section view taken at lines 3a-3a in FIG. 3.

FIG. 4 is a diagrammatic side view of another of the invention.

FIG. 5 is a diagrammatic side view of yet another embodiment of the invention. 7

In FIGS. l-5 certain well-known portions of relays have been omitted for sake of clarity and convenience of illustration.

FIGS. 6a to 6e are views useful in illustrating how typical conductive resilient wire pads used with the various embodiments of the invention may be formed.

FIG. 7 is a diagrammatic side view of afurther form of relay constructed in accordance with the invention.

FIG. 8 is a cross section view through a modified form of conductive resilient pad contact includingan elastomer base.

FIG. 9 is a cross section view through a modified form of conductive resilient pad contact which comprises a knitted wire boot.

FIG. 10 diagrammatically illustrates one use of the invention in a rotary cam-operated switch arrangement.

The improved relay shown in FIG. 1 comprises a base (not shown) having an electromagnet l2 fixedly mounted thereon.

embodiment The ends of the electromagnet coil are connected to stationary terminal posts 13 and 14. A soft-iron armature bar 16 is pivotally mounted at on a shaft (not shown) extending normal to the plane of FIG. I. A movable contact arm 18 is riveted to armature 16 at 19, 19, and flexible wire 20 connects contact arm 18 to terminal post 22. A tension spring 24 is connected between a tab or armature 16 and adjustment screw 25 threaded in fixed post 26 and locked in place by lock nut 27. The relay is shown with a stationary normally open contact 28 anda stationary normally closed contact 30, both of which are shown as identical types in FIG. 1. Stationary contact 28 is shown bolted with nut 32 onto a stationary bar or lug 29 which extends upwardly from the base (not shown), and stationary contact 30 is similarly bolted with nut 33 to a similar stationary lug 31. A wire 34 bolted between lug 29 and head 40a of stationary contact 28 extends to terminal post 36. When electromagnet 12 is energized, it will be seen that-arm l8 and sta tionary contact 28 complete a circuit between tenninal posts 22 and 36, to which an external circuit (not shown) may be connected.

Referring now to FIG. la, wherein contact 28 is shown in greater detail, the cohtact will be seen to comprise a rigid metal (preferably copper) boltlike piece 40 having a cylindrical head portion 40a and a shank portion 40b. A length of the exterior portion of shank 40b is threadedto accommodate nut 32 (FIG. 1). A that cylindrical bore 40c in the shank contains coilspring 42 and a portion of a reciprocating slidingly movable plunger 44. Plug 46 threaded into bore 40c retains spring 42 and plunger 44 within the bore, which is reduced in diameter at its upper end to limit upward motion of plunger 44, the upper end of which extends through head 400. A flexible wire 45 is shown soldered at one end to plunger 44 and at its other end to plug 46. Solderedor welded, or otherwise attached to head 40 both mechanically and electrically, is a doughnut or ring-shaped, conductive, resiliently compressible pad 47 having a central aperture through which the outer end of reciprocating plunger 44 extends. When the contact is open, spring 42 urges plunger 44 upwardly so that the tip or end surface of plunger 44 lies above the outer or upper surface of pad 47, which is then in its expanded or relaxed condition.

When electromagnet coil 12 is energized, armature l6 swings counterclockwise as viewed in FIG. I, translating movable contact arm 1.8 toward stationary contact 28. Am 18 first strikes the end of plunger 44, pushing plunger 44 down into shank 40b against the force of spring 42, and then further travel of arm l8'cornpres'ses pad 47, so that both plunger 44 and pad 47 make electrical contact with arm 18. As arm 18 compresses pad 47, many of the pieces or sections of the wire tangle forming pad 47 tub or scrape against each other, thereby damping out contact bounce. The edges of the wire forming the outer surface of pad 47 also move as the pad is compressed, tending to wipe clean a ring-shaped area on arm When the energization of electromagnet 12 is interrupted, spring 24 rotates arm 18 clockwise as viewed in FIG. 1. During a first portion of the clockwise movement of arm 18, pad 47 expands from its therefore compressed condition and spring 42 simultaneously moves plunger 44 outwardly, so that the end of the plunger remains in contact with arm 18. After pad 47 has fully expanded further movement of arm 18 away from stationary contact 28 results in pad 47 losing contact with arm 18, but with the end of plunger 44 still contacting arm l8. When arm 18 has moved far enough to'allow spring 42 to move plunger 44 to itsoutward limit position, further movement of arm 18 will open the circuit between plunger 44 and arm 18. Because arm 18 ceases to touch pad 47 before it ceases to touch plunger 44, any arcing which occurs, such as that due to substantial inductance in the external circuit, will occur between arm 18 and plunger 44, and not to the fine wires of pad 47. Because plunger 44 may have a cross section providing much more current-carrying capacity than that of the individual wires of pad 47, a substantial arc between arm 18 and plunger 44 will cause no damage.

Under certain operating conditions, the repeated occurrence of substantial arcs between arm 18 and plunger 44 will tend to pit either the end of the plunger or a portion of the surface of arm 18, or both of them, so that plunger 44 and arm 18 tend to make unreliable point contact rather than area contact when the relay is energized. While such pitting might seriously M interfere with the operation of a conventional relay, it causes little or no trouble with the relay of FIG. 1, since the major part of the current fiows between arm 18 and pad 47 after the relay contact pair has'closed. Thus the relay of FIG. 1 operates 18a, translated counterclockwise by energization of coil 12 to attract armature 16, and returned clockwise by return spring 24'upon deenergization of coil 12. Arm 18 also carries ferromagnetic pad 59. Stationary contact arm 58 fixedly mounted on the relay base (not shown) carries conductive resilient pad 47. A resilient blade arm 60 welded at 60a to stationary arm 58 carries permanent magnet 61 on its other end, magnet 61 protmding through a hole in arm 58. When coil 12 is energized and arm 18 moves counterclockwise, surface 18b on arm 18 eventually engages pad 47 and begins to compress pad 47. After pad 47 has been substantially compressed, magnetic pad 59 will have moved close enough to permanent magnet 61 that the two are strongly attracted toward each other, so that they snap together, with blade 60 bending to allow magnet 61 to move slightly rightwardly as viewed in FIG. 2. When coil 12 is later deenergized, movable arm 18 is moved clock wise by return spring 24. During the first portion of such clockwise motion of arm 18,-pad 47 is decompressed, and permanent magnet 61 moves rightwardly, remaining in contact with magnetic pad 59. The spring constant of spring 24 is arranged to be far greater than that of blade 60. After pad 18a has completely cleared or lifted off of the surface of resilient pad 47, the deflection force of spring arm 60 caused by rightward movement of magnet 61 becomes greater than the attractive force between magnet 61 and pad 59, so that spring 60 rapidly snaps free from pad 59. Because resilient pad 47 has been completely disengaged before magnet 60 snaps free of pad 59, it will be seen that all arcing which occurs during the opening of the contact pair will occur between magnet 61 and pad 59, thereby preventing any damage to the fine wires of pad 47. Pad 18b on arm 18 may comprise a precious metal surface, if desired. Magnet 61 and magnetic pad 59 may comprise soft iron, or Alnico, for example. If desired, portions or all of these two elements may be copper plated to reduce their resistance.

It will become apparent without detailed explanation, that the locations of pads 47 and 18b may be interchanged, with resilient pad 47 carried on movable arm 47 without departing from the invention or significantly affecting the operation of the device of FIG. 2. Similarly, spring 60 and magnet 61 may be carried on movable arm 18 and magnetic pad then affixed to stationary arm 58. Thirdly, the element 61 carried on arm 60 may be unmagnetized (but magnetic) if element 59 is magnetized, or if desired, both elements 59 and 61 may be magnetized with their poles oriented so that they attract.

FIGS. 3 and 3a illustrate an improved resilient pad contact which may be used in a wide variety of relay and contactor applications, either on fixed or movable contact arms, or in pairs on both such arms. In FIG. 3 the new contact is shown mounted on arm 60 to make electrical contact with arm 61 upon appropriate relative motion between the two arms. The contact comprises a rigid member, formed of copper, for example, having a cylindrical head portion 62a and a cylindrical partially threaded shank portion 62b. The shank extends through a hole in arm 60 and carries nut 63. A resilient con- .ductive wire pad 64 welded or soldered atop head 62a comprises a wire tangle or mesh pad comprised of many interengaging sections or turns of wire. Pad 64 is shown generally cylindrical in outer configuration, but provided with an internal cavity 640 which also may be cylindrical. Compression pring means, such as a small coil spring (not shown), may be inserted inside cavity 64a, if desired, acting between head 62a and the resilient pad at the top of the cavity. A rigid and solid contact button or pad 65 preferably fonned of copper is soldered or welded atop pad 64, and a ring-shaped groove 64b is preferably provided in pad 64 surrounding button 65.

Upon motion of arm 60 toward arm 61 or motion of ann 61 toward arm 60, button 65 first makes contact with arm 61. Upon continued relative motion of the two anns, the pressure on button 65 tends to collapse cavity 64a, pushing wire downwardly to fill that space, and pushing button 65 down partially into pad 64, until the upper edge of button 65 is even with the ring-shaped wire-edge surface 64c of pad 64. Upon further such motion of the arms, arm 61 tends to further compress pad 64. Groove 64b, which is optional, serves to isolate movement of button 65 from surface 64c, so that any tendency for button 65 to tilt or cock does not cause surface 640 to tilt or cook. Upon opening of the contact pair shown in FIG. 3, as arm 61 first lifts upwardly both surface 64c and button 65 rise. Eventually the portions of pad 64 adjacent surface 64c become fully expanded and arm 61 loses contact with surface 640, but button 65 continues to be urged upwardly and to remain in contact with arm 61. Eventually cavity 64a is reformed, upward movement of button 65 ceases, and arm 61 breaks contact with button 65. Because any arcing takes place between button 65 and arm 61, the fine wire sections which form surface 64c are not damaged by the arcing.

In FIG. 4 energization of electromagnet 12 pivots arm 70 about the axis of a shaft located at 70a against the force of return or tension spring 24 and urges conductive resilient pad 47 into contact with pad 71 on fixed contact. bar 72; A second pivot arm 73 pivoted on a fixed shaft (not shown) at 73a is engaged by one end of compression spring 74, the other end of which is fixedly fastened to the relay base (not shown) at 74. Wire 79 interconnects arms 70 and 73. In the deenergized condition shown in FIG. 4, compression spring 74 urges arm 73 counterclockwise, holding it against finger 76 which extends from arm 70 into the path of rotation of arm 73. Energization of electromagnet 12 rotates armature l6 and arm 70 clockwise about the axis at 700, and finger 76 will be seen to urge arm 73 clockwise about the axis at 73a. As the face of resilient pad 47 engages pad 71, finger 76 rotates arm 73 past a dead center" position in which the lower section of arm 73 extends between axes 73a and 75, so that compression spring 74 then suddenly urges arm 73 clockwise instead of counterclockwise, thereby rapidly rotating arm 73 so that its pad 73b engages pad 77 on fixed terminal post 72. Arm 73 and spring 74 are shown in such a position in dashed lines in FIG. 4. Upon deenergization of magnet 12 tension spring 24 returns arm 70 in a counterclockwise direction. After arm 70 has rotated counterclockwise sufficiently for resilient pad 47 to clear pad 71, finger 78 on arm 70, which finger also extends into the path of rotation of arm 73, begins to urge arm 73 clockwise, and when arm 73 has been rotated past the dead center position, compression spring 74 rapidly snaps it counterclockwise, breaking contact between pads 73!; and 77. As in previous embodiments, all arcing occurring as the contact pairs open will be seen to occur between rigid contacts, and not to the fine wires of a resilient pad. The relay of FIG. 4 may be provided with a stop (not shown) to limit counterclockwise travel of arm 70, or, as will be apparent, a further resilient conductive pad and fixed contact may be provided in similar fashion on the opposite side of arm 70 to provide a double-throw relay.

In the device of FIG. 5 energization of electromagnet coil 12 to attract armature 16 pivots movable contact arm 18 clockwise about a pivot shaft (not shown) located at point 18a, against the force of return spring 24, one end of which is place between pairs 36a-44a.

attached to a tab on arm 18 and the other end of which is held stationary by adjustment screw 25 threaded into stationary lug; 26. Clockwise motion of arm 18 compresses conductive resilient pad 47 against stationary contact bar 72. In FIG. 5 arm 18 is shown in an intermediate position where pad 47 almost touches bar 72. Extending from arm 18 is a thin phosphor bronze blade spring 18b which carries rigid contact 44a. In the position shown in FIG. 5 blade 18b is shown slightly flexed with contact 44a making electrical contact with stationary contact 36a, even thoughIpad 47 is not contacting bar 72. Thus rigid contact pair 360 44a makes contact before pair 47-72 when coil 12 is energized andbreaks after pair. 47-72 when coil 12 is deenergized, so that all arcing takes Blade spring 18b preferably isa weak spring compared to resilient pad 47. While the compression of blade spring 18b prior to engagement of pad 47 will be seen to affect contact bounce, it will be seen that vibration of arm 18 due 'to the resilience of spring arm 18b will tend to be dampened'because of the low coefficient of restitution of pad 47. The addition of spring l8has the'effect' of increasing the coefficient of restitution of the movable portion of the relay,

so that provision of a very low coefficient of'restitution in pad 47 is particularly desirable in an arrangement such as that of FIG. 5.

In each of the embodiments of the invention the resilient pad contacting area which results when the pad contact closes may be made to be greater, the same as, or less than the mating contact area between the rigid or hard surface" auxiliary contact pair, so that the current flow through the pad is greater, the same as, or less than the current through the auxiliary contact pair while the two pairs are closed.

Referring now to FIGS. 6a-6e, a conductive 6e padsuch as that shown at 47 in FIG. 1a may be formed by covering a doughnut or ring-shaped wire tangle such asthat shown in FIG. 6e with a formed wire mesh covering of the type shown in FIG. 60. A length of springy beryllium copper wire or phosphor bronze wire, preferably of a gauge between 036 and 044, and preferably with a noncircular cross section, is trained back and forth and up and down in a cavity such as that shown at 80 in FIG. 6d and periodically tamped or partially bent by introduction of male die 81 as successive lengths of the wire are fed into the cavity, eventually forming'a-springy wire tangle having generally the shape shown in FIG. 6e. A woven wire cloth disc having conductive wire threads (e.g. also 036 to 044 gauge, for example) running in warp and fill directions is placed in the tamping and forming die shown in FIG. 6b to form a wire mesh shape of the type shown in FIG. 6c. The wire tangle of FIG. 6e is made with a size such that it will fit snugly into the woven wire covering of FIG. 6c, thereby forming a pad suitable for use as pad 47 of FIG. la. In some applications of the invention a wire tangle may be used without a wire mesh covering.

. FIG. 7 diagrammatically illustrates a modified version of the basic idea of FIG. 2 wherein magnetic rne ans hold the auxiliary contact closed until after the resilient pad contact opens. In FIG. 7 energization of a first winding of electromagnet 12', by application of voltage to terminals 13 and 14 attracts armature 16 to pivot movablecontact arm 18 clockwise about pivot point 180, against the force of leaf return spring 24', so that resilient pad 47 is compressed on stationary contact bar 72. Spring arm 85 is carried on arm 18 but insulated therefrom by insulation 86, and a magnetic plunger 87 which'extends within electromagnetic 12a is attached tothe free end of spring 85 by further insulation 88, so that spring 85 and piece 87 rotate with arm 18 as contact pair 47-72 closes. Electromagnet coil 12' also includes a second winding on the same core, the ends of the second winding being shown at 89 and 90. The second winding is connected to electromagnet 12a through a semiconductor diode rectifier 91.

When coil 12 is energized, the increase in flux in coil 12 induces a voltage in the second winding having'a polarity such that current flow through electromagnet 12a isblocked. When energization of coil 12' is interrupted, however, the decrease plunger 87 rightwardly as viewed in in flux in magnet 12' induces a voltage having an opposite polarity, so that'magnet 12a is temporarily magnetized. The temporary magnetizing of magnet 12a temporarily attracts FIG. 7 into electromagnet 12a, flexing spring and causing auxiliary contact pair 85l-l8b to close part of the time during which arm 18 rotates counterclockwise. After pwa ears contact 72, mafia; o flux in electromagnet 12a allows auxiliary contact pair 85a-l8 b to open. Again it will be seen that all arcing occurring during opening will occur across the auxiliary contact-pair. The arrangement of FIG. 7 differs from most of the previous embodiments in that the auxiliary contact pair is closed only briefly while the resilient pad contact is opening, and not during the entire interval during which the resilient pad contact is engaged.

Each of the" resilient pads shown in the various embodiments, rather than carrying a oven mesh cover to preserve their basic shape, mayiinstead have one face fixed in a layer of elastomer, such as that shown at 47d in FIG. 8, with one or more ends of the wire passing through the elastomer to be soldered, or welded or otherwise fastened to the movable or stationary arm 18f upon which the wire pad is mounted. The wire ends may bepulled through holes 183, 18g in the arm and soldered'or welded on the other side, for example, to hold the pad snugly on the arm.

FIG. 9 illustrates a conductive resilient pad comprising a hollow knitted, flexible wire boot," knitted from 044 gauge beryllium copper wire, for example to provide a mushroomshaped boot or cap. The boot fits loosely over the head of stud 40. When nut 32ls tightened, a circular lip or edge of the boot will be tightly compressed between stud 40 and arm 18, so that no soldering'or welding is required in order to make effective electrical contact to the boot. The 'arm of the head of stud 40 is preferably undercut and rounded as shown. The crown of the boot is preferably knitted to have a substantial thickness, and loosely knitted. With the boot being made oversize, the crown of the boot tends to be held away from the top of the stud' by the resilience of the wire when nut 32' is tightened, thereby forming a small cavity such as that shown in FIG. 9. It will be seen that the boot may be easily and rapidly replaced should it become worn after long usage.

FIG. 10 diagrammatically illustrates the use of the invention in a cam-operated switch, which is shown for illustration in FIG. 10 as comprising anignition breaker point set such as is used with high-performance internal combustion engines. Cam 101 is rotated in conventional manner in synchronism with the engine crankshaft by means not shown, and the corners or lobes on cam 101 periodically rotate arms 102 and 103, which are springbiased toward cam 101. The cam followers I05 and 106 are differently offset from the centerline of cam 101, so that contact set 108, which includes a conductive resilient pad 109, both closes and opens before rigid contact set 110, rigid contact set being arranged to close before contact set 108 opens. Contact sets 108 and 110 are wired in arallel as shown. The stationary portions of contact sets 108 and 110 are grounded. The overlapping closure times ofthe two contact sets increases the effective "dwell" period and thereby increases ignition coil efficiency. During closure of contact set 108 flux builds up in the primary winding 112 of ignition coil I13. Rigid contact set 110 then closes and flux buildup continues. Contact set 108 then opens but rigid contact set 110 remains closed and flux buildup still continues. Throughout the time that either contact set is closed capacitor C- will be seen to' beshorted, with both of its terminals connected to ground. Finally rigid contact set 110 opens and the collapse of flux in the primary winding of ignition coil 113 in conjunction with the'charge of capacitor C causes the generation of a-high voltage inthe secondary winding of the coil. As contact set 110 begins to open, the increase in voltage across the primary winding clue to the inductance of the coil 113 is limitedby the charging of capacitor C, thereby minimizing arcing at contact set 110. By the time capacitor C is fully charged contact set 1 10 is open wide enough to avoid a substantial are at that contact set. When capacitor C is fully charged current through the primary wining stops and the flux has collapsed to zero. The discharge of capacitor C in an opposite direction through the primary winding then causes flux buildup in an opposite direction, which increases the voltage induced in the secondary winding. Because contact set 108 including the resilient pad contact 109 always opens before the rigid contact set 110, all arcing occurs across the rigid contact set. in prior art systems involving only rigid contacts, contact bounce is frequently a problem. In the system shown the resilient pad provides a more reliable contact to initiate ignition coil flux buildup. The resilient pad 109 will be seen to be free from damage due to arcing until the rigid contacts are worn so badly that they never close.

The invention is applicable as well to various other forms of cam-operated switches, including, for example, cam-operated switches of the type used in defrost timers of refrigerators, where very small motors are used to rotate a cam and reliable switch closure and opening must be effected without imposing substantial torque loads on such motors.

A movable relay armature of a multipole relay may translate a plurality of electrically separate movable contacts, of course, and the application of the invention to multipole relays will be apparent to those skilled in the art in view of the above disclosure. While the invention has been principally illustrated in connection with electromagnet switches wherein an electromagnet causes a movable contact arm to pivot, it will be readily apparent that the invention is applicable as well to switches where an electromagnet instead translates a movable contact in a linear manner, applicable to switches where motive means other than simple electromagnets are used, applicable to switches where the motive means pivots or translates both of a pair of mating contacts rather than moving only one of them relative to a fixed other one, and applicable as well to manually operated switches.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description are efficiently attained, and since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An electrical switch, comprising, in combination: first and second electrical contact members; means for providing relative motion between said members to engage and disengage said members, at least one of said contact members including conductive spring means adapted to be flexed as said contact members are engaged and disengaged, said conductive spring members having a plurality of wire portions arranged to frictionally rub each other as said conductive spring means is flexed, and a pair of auxiliary contacts each having rigid contact surfaces, one of said auxiliary contacts being connected to said first electrical contact member and the other of said auxiliary contacts being connected to said second electrical contact member so that disengagement of said first and second electrical contact members causes said rigid contact surfaces to disengage after disengagement of said fist and second electrical contact members, whereby arcing occurring during disengagement occurs between said rigid contact surfaces, said first electrical contact member and said one of said auxiliary contacts being fixedly mounted relative to each other, said second electrical contact member comprising a first arm movable relative to said second electrical contact member, said other of said auxiliary contacts comprising a second arm movable relative to said one said auxiliary contacts, second spring means biasing said second arm in either direction away from the reference position; and means mechanically connected to said first arm for moving said second arm in opposite directions past said reference position as said first arm is moved to engage and disengage said second electrical contact member. t I

2. An electrical switch, comprising, in combination: first and second electrical contact members; means for providing relative motion between said members to engage and disengage said members, at least on said contact members including spring means adapted to be flexed as said contact members are engaged and disengaged, said conductive spring means having a plurality of wire portions arranged to frictionally rub each other as said conductive spring means is flexed, and a pair of auxiliary contacts each having rigid contact surfaces, one of said auxiliary contacts being connected to said first electrical contact member and the other of said auxiliary contacts being connected to said second electrical contact member so that disengagement of said first and second electrical contact members causes said rigid contact surfaces to disengage after disengagement of said first and second electrical contact members, whereby arcing occuring during disengagement occurs between said rigid contact surfaces, said conductive spring means mounted on said one of said electrical contact members comprising a resilient pad having a surface adapted to engage the other of said electrical contact members, and one of said auxiliary contacts comprising rigidv pad means mounted on said resilient pad, with said rigid contact surface of said rigid pads means extending beyond said surface of said resilient pad when said electrical contact members are disengaged.

3. An electrical switch, comprising, in combination: first and second electrical contact members; means for providing relative motion between said members to engage and disengage said members, at least one of said contact members including conductive spring means adapted to be flexedas said contact members are engaged and disengaged, said conductive spring means having a plurality of wire portions arranged to frictionally rub each other as said conductive spring means is flexed, and a pair of auxiliary contacts each having rigid contact surfaces, one of said auxiliary contacts being connected to said first electrical contact member and the other of said auxiliary contacts being connected to said second electrical contact member so that disengagement of said first and second electrical contact members causes said rigid contact surfaces to disengage after disengagement of said first and second electrical contact members, whereby arcing occurring during disengagement occurs between said rigid contact sur faces, said means for providing relative motion including a first electromagnet means adapted upon energization to engage said first and second electrical contact members; a second electromagnet means adapted upon energization to engage said pair of auxiliary contacts; and means responsive to deenergization of said first electromagnet means for temporarily energizing said electromagnet means. 

1. An electrical switch, comprising, in combination: first and second electrical contact members; means for providing relative motion between said members to engage and disengage said members, at least one of said contact members including conductive spring means adapted to be flexed as said contact members are engaged and disengaged, said conductive spring members having a plurality of wire portions arranged to frictionally rub each other as said conductive spring means is flexed, and a pair of auxiliary contacts each having rigid contact surfaces, one of said auxiliary contacts being connected to said first electrical contact member and the other of said auxiliary contacts being connected to said second electrical contact member so that disengagement of said first and second electrical contact members causes said rigid contact surfaces to disengage after disengagement of said fist and second electrical contact members, whereby arcing occurring during disengagement occurs between said rigid contact surfaces, said first electrical contact member and said one of said auxiliary contacts being fixedly mounted relative to each other, said second electrical contact member comprising a first arm movable relative to said second electrical contact member, said other of said auxiliary contacts comprising a second arm movable relative to said one said auxiliary contacts, second spring means biasing said second arm in either direction away from the reference position; and means mechanically connected to said first arm for moving said second arm in opposite directions past said reference position as said first arm is moved to engage and disengage said second electrical contact member.
 2. An electrical switch, comprising, in combination: first and second electrical contact members; means for providing relative motion between said members to engage and disengage said members, at least on said contact members including spring means adapted to be flexed as said contact members are engaged and disengaged, said conductive spring means having a plurality of wire portions arranged to frictionally rub each other as said conduCtive spring means is flexed, and a pair of auxiliary contacts each having rigid contact surfaces, one of said auxiliary contacts being connected to said first electrical contact member and the other of said auxiliary contacts being connected to said second electrical contact member so that disengagement of said first and second electrical contact members causes said rigid contact surfaces to disengage after disengagement of said first and second electrical contact members, whereby arcing occuring during disengagement occurs between said rigid contact surfaces, said conductive spring means mounted on said one of said electrical contact members comprising a resilient pad having a surface adapted to engage the other of said electrical contact members, and one of said auxiliary contacts comprising rigid pad means mounted on said resilient pad, with said rigid contact surface of said rigid pads means extending beyond said surface of said resilient pad when said electrical contact members are disengaged.
 3. An electrical switch, comprising, in combination: first and second electrical contact members; means for providing relative motion between said members to engage and disengage said members, at least one of said contact members including conductive spring means adapted to be flexed as said contact members are engaged and disengaged, said conductive spring means having a plurality of wire portions arranged to frictionally rub each other as said conductive spring means is flexed, and a pair of auxiliary contacts each having rigid contact surfaces, one of said auxiliary contacts being connected to said first electrical contact member and the other of said auxiliary contacts being connected to said second electrical contact member so that disengagement of said first and second electrical contact members causes said rigid contact surfaces to disengage after disengagement of said first and second electrical contact members, whereby arcing occurring during disengagement occurs between said rigid contact surfaces, said means for providing relative motion including a first electromagnet means adapted upon energization to engage said first and second electrical contact members; a second electromagnet means adapted upon energization to engage said pair of auxiliary contacts; and means responsive to deenergization of said first electromagnet means for temporarily energizing said electromagnet means. 